Low Temperature Atmospheric Pressure Plasma Research Articles

On Plasma Activated Acetyl Donors: Comparing the Antibacterial Efficacy of Tetraacetylethylenediamine and Pentaacetate Glucose

The study compares how acetyl donor molecules tetraacetylethylenediamine (TAED) and pentaacetate glucose (PAG) improve the antibacterial efficacy of solutions activated with a low-temperature atmospheric-pressure argon plasma jet. Plasma activation of solubilised TAED and PAG produce solutions with different chemical compositions and oxidative potentials. Both acetyl donor molecules enhance the hydrogen peroxide (H2O2) concentration in solution with TAED being more effective compared to PAG. However, PAG is more effective at forming peracetic acid (PAA) from reaction of its acetyl donor groups with plasma generated H2O2. The enhanced oxidative potential of plasma activated TAED and PAG solutions were shown to significantly improve bactericidal activity against common wound pathogens Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus compared to plasma activated water produced without acetyl donors. Furthermore, the oxidative capacity of plasma activated PAG was least affected by the bacterial oxidative defence enzyme catalase, attributed to the high concentration of PAA produced in this formulation. Overall, the above data show that acetyl donors may help improve next generation of antimicrobial formulations produced by plasma, which might help combat increasing problems of antimicrobial resistance.

Nonthermal atmospheric plasma reactors for hydrogen production from low-density polyethylene

Hydrogen is largely produced via natural gas reforming or electrochemical water-splitting, leaving organic solid feedstocks under-utilized. Plasma technology powered by renewable electricity can lead to the sustainable upcycling of plastic waste and production of green hydrogen. In this work, low-temperature atmospheric pressure plasma reactors based on transferred arc (transarc) and gliding arc (glidarc) discharges are designed, built, and characterized to produce hydrogen from low-density polyethylene (LDPE) as a model plastic waste. Experimental results show that hydrogen production rate and efficiency increase monotonically with increasing voltage level in both reactors, with the maximum hydrogen production of 0.33 and 0.42 mmol/g LDPE for transarc and glidarc reactors, respectively. For the transarc reactor, smaller electrode-feedstock spacing favors greater hydrogen production, whereas, for the glidarc reactor, greater hydrogen production is obtained at intermediate flow rates. The hydrogen production from LDPE is comparable despite the markedly different modes of operation between the two reactors.

Bactericidal effects of low-temperature atmospheric-pressure air plasma jets with no damage to plant nutrient solutions

The bactericidal effects of air plasma jets produced with a twisted wire-cylindrical electrode configuration were clarified in terms of plasma-induced damage to plant nutrient solutions. The bacterial suspensions were directly irradiated with air plasma jets using a low gas flow rate, which was shown to significantly inactivate the bacteria suspended in the solutions without reducing the nutrient concentrations. However, the plasma irradiation time required for inactivation depended on the type of bacteria; Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) were inactivated in 20–30 s, while Staphylococcus aureus (S. aureus) required 7 min. The inactivation of E. coli and B. subtilis decreased with increasing air gas flow rate, whereas the inactivation of S. aureus was independent of the rate. The inactivation could be attributed to a greater number of reactive oxygen and nitrogen species (RONS) from the air plasma jet, including O2 molecules in the feeding gas attaching to the bacterial suspension surface, which do not harm the nutrient components. This can be derived from the results; the air-plasma-jet-activated nutrient solutions (RONS introduced in the solutions) and the N2 plasma jets had only a limited inactivation effect on the bacteria suspended in the solutions.

Atmospheric plasma jet for surface treatment of biomaterials

A direct current (DC) powered low-temperature atmospheric pressure plasma (LTAPP) jet device was built and used to sterilize Escherichia coli (E. coli) bacteria. The plasma jet’s general properties, such as length and temperature, were first tested and found to be strongly related to the plasma jet’s operational flow mode (laminar or turbulent flow). The optical emission spectra of various gas mixtures were measured to confirm the presence of active radicals, which is critical for sterilization success. Pure helium gas or a combination of helium with a small percentage of oxygen (6.25%) was found to have the highest intensities of bactericidal species such as atomic oxygen (O) and hydroxide (OH). These mixtures were then used to treat E. coli bacteria previously grown in a Petri dish. Sterilization was accomplished by repeatedly treating the bacteria for 10 s for 5–10 rounds for short periods. The best results were obtained when the bacteria had enough time to rest between rounds.

Roles of the reaction boundary layer and long diffusion of stable reactive nitrogen species (RNS) in plasma-irradiated water as an oxidizing media — numerical simulation study

The concentration distributions of chemically reactive species in water exposed to low-temperature atmospheric-pressure plasma (APP) have been studied with one-dimensional numerical simulations. Highly reactive species supplied from an APP to the water surface all react in the “reaction boundary layer,” i.e. a thin layer with a thickness of about 100 nm on the solution side of the interface, and are converted to stable species. This study quantitatively shows that, in the case of pure water irradiated by an APP, the simultaneous presence of H2O2, NO2 −, and O3 in the solution is the only cause to make it an oxidizing medium as they continuously produce ONOOH and HO3, which then decay to generate OH radicals in the solution bulk. ONOOH and its accompanying HO2NO2 have much longer diffusion lengths than HO3 and therefore their diffusion can also contribute to the oxidizing capability of the solution.

Current Advancements in the Molecular Mechanism of Plasma Treatment for Seed Germination and Plant Growth.

Low-temperature atmospheric pressure plasma has been used in various fields such as plasma medicine, agriculture, food safety and storage, and food manufacturing. In the field of plasma agriculture, plasma treatment improves seed germination, plant growth, and resistance to abiotic and biotic stresses, allows pesticide removal, and enhances biomass and yield. Currently, the complex molecular mechanisms of plasma treatment in plasma agriculture are fully unexplored, especially those related to seed germination and plant growth. Therefore, in this review, we have summarized the current progress in the application of the plasma treatment technique in plants, including plasma treatment methods, physical and chemical effects, and the molecular mechanism underlying the effects of low-temperature plasma treatment. Additionally, we have discussed the interactions between plasma and seed germination that occur through seed coat modification, reactive species, seed sterilization, heat, and UV radiation in correlation with molecular phenomena, including transcriptional and epigenetic regulation. This review aims to present the mechanisms underlying the effects of plasma treatment and to discuss the potential applications of plasma as a powerful tool, priming agent, elicitor or inducer, and disinfectant in the future.

Potential formation on floating metal plate treated by low-temperature atmospheric pressure plasma jet

In the biomedical applications using low-temperature atmospheric pressure plasmas, charging on surface of the targets could play an important role. In this study, we have investigated potential formed on an electrically floating copper plate treated by a low-temperature atmospheric pressure helium plasma jet. The potential of the copper plate was measured by an electrostatic sensor in a non-contact manner. It was found that the potential on the copper plate could be controlled from 200 to −600 V by changing the distance between the nozzle of plasma device and the surface of copper plate. We discussed the charging mechanism such as collection of charged particles and several processes of electron emission including thermionic, field emission, secondary electron emission, and photoelectric processes.

Resin Cement-Zirconia Bond Strengthening by Exposure to Low-Temperature Atmospheric Pressure Multi-Gas Plasma.

The purpose of this study was to investigate the effect of gas species used for low-temperature atmospheric pressure plasma surface treatment, using various gas species and different treatment times, on zirconia surface state and the bond strength between zirconia and dental resin cement. Three groups of zirconia specimens with different surface treatments were prepared as follows: untreated group, alumina sandblasting treatment group, and plasma treatment group. Nitrogen (N2), carbon dioxide (CO2), oxygen (O2), argon (Ar), and air were employed for plasma irradiation. The bond strength between each zirconia specimen and resin cement was compared using a tension test. The effect of the gas species for plasma irradiation on the zirconia surface was investigated using a contact angle meter, an optical interferometer, an X-ray diffractometer, and X-ray photoelectric spectroscopy. Plasma irradiation increased the wettability and decreased the carbon contamination on the zirconia surface, whereas it did not affect the surface topography and crystalline phase. The bond strength varied depending on the gas species and irradiation time. Plasma treatment with N2 gas significantly increased bond strength compared to the untreated group and showed a high bond strength equivalent to that of the sandblasting treatment group. The removal of carbon contamination from the zirconia surface and an increase in the percentage of Zr-O2 on the zirconia surface by plasma irradiation might increase bond strength.

Investigation of sterilization by a microwave-generated low-temperature atmospheric pressure plasma jet

An investigation of sterilization by a low-temperature microwave-generated atmospheric pressure plasma jet (MAPPJ) is presented. Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and yeast Saccharomyces species (Saccharomyces sp.) at 1.0 × 103 and 1.0 × 104 cfu/mL dilutions are investigated and fungi tested experimentally. The MAPPJ is generated by several watt continuous-wave microwaves and Ar gas, and direct treatment of the bacteria by a programmable planar XY motorized translation stage. After several minutes of plasma treatment, the number of bacterial colonies was sufficiently reduced and found to be nearly zero, and bare ozone and nitrogen dioxide were observed. This investigation shows that plasma sterilization would be a novel application for solid-state microwave power sources.

大腸がん細胞に対する大気圧低温プラズマ照射培地による細胞障害の検討

Recently, the application of atmospheric pressure low temperature plasma to the medical field is expected, and the growth inhibitory action of cancer cells is indicated in the preceding research. In this study, colorectal cancer with many cases and deaths was noticed. The effect of plasma on colorectal cancer cells was evaluated by culturing colorectal cancer cells in a medium irradiated with atmospheric pressure low temperature plasma, expecting to induce proliferation inhibition or cell death. In addition, in this study, in order to examine the components affecting colorectal cancer cells, the concentration measurement of reactive oxygen species generated in the solution irradiated with plasma using the absorbance method was carried out. And, the mechanism of the cell reduction of the colorectal cancer cell induced by plasma was investigated.

Исследование морфофункциональных свойств биотканей ( in vivo) при воздействии низкотемпературной плазменной струи атмосферного давления

The results of spectral-fluorescent and diffuse-optical studies of living tissues under the effect of low-temperature atmospheric pressure plasma jet in a mixture of air and argon are presented. Potential fluorophores are identified and coefficients of optical absorption and transport scattering of tissues are determined. It was revealed plasma jet irradiation of tissue leads to an increase in the intensity of fluorescence and the diffuse reflection coefficient, which is linked with a twofold increase in the transport scattering coefficient and a change in the concentration of endogenous chromophores – a reducing water content, lipids and bilirubin to 20%, and an increasing levels of oxygen saturation to 10%. On the basis of the analysis, it is shown that the therapeutic effect of low-temperature plasma can be associated with increased antioxidant protection and the development of compensatory dehydration processes.

Study on the effect of low-temperature atmospheric pressure plasma jet on the morphofunctional properties of living tissues (in vivo)

The results of spectral-fluorescent and diffuse-optical studies of living tissues under the effect of low-temperature atmospheric pressure plasma jet in a mixture of air and argon are presented. Potential fluorophores are identified and coefficients of optical absorption and transport scattering of tissues are determined. It was revealed plasma jet irradiation of tissue leads to an increase in the intensity of fluorescence and the diffuse reflection coefficient, which is linked with a twofold increase in the transport scattering coefficient and a change in the concentration of endogenous chromophores --- a reducing water content, lipids and bilirubin to 20%, and an increasing levels of oxygen saturation to 10%. On the basis of the analysis, it is shown that the therapeutic effect of low-temperature plasma can be associated with increased antioxidant protection and the development of compensatory dehydration processes. Keywords: biological tissues, cold plasma, probing, spectroscopy, fluorescence, diffuse reflection, optical coefficients, light scattering, biochemistry, morphology.

ZnO nanofibers prepared by plasma assisted calcination: Characterization and photocatalytic properties

The ZnO nanofibers (ZnO-NF) have been fabricated by the novel approach of plasma assisted calcination using the low-temperature atmospheric pressure plasma generated by diffuse coplanar surface barrier discharge (DCSBD). The electrospun polyvinyl pyrrolidone/zinc acetate fibers were exposed to DCSBD plasma before the thermal processing at different temperatures (400 °C,500 °C and 600 °C) and characterized in term of chemical composition and morphological structure by ATR-FTIR, XPS, SEM, XRD, and BET analysis. The photocatalytic activity of prepared ZnO-NF has been investigated under UV-radiation using methylene blue and the kinetics of photodegradation and reusability were studied. The results showed that initial removal of organic matrix at low-temperature by application of plasma leads to better formation of Zn-O even at lower calcination temperature. The plasma pre-treated (PT) fibers exhibit lower diameter of final products and helps to preserve a well-defined fibrous structure during thermal processing. The ZnO-NF prepared by a combination of plasma treatment and thermal processing showed significantly higher photodegradation activity and the difference was higher with decreasing calcination temperature. The highest rate constants were reached for fibers calcined at 600 °C with and without plasma treatment – kPT = 0.0149 min−1, kNT = 0.0107 min−1, respectively. The slight improvement of re-usability in cyclic photodegradation was observed on samples calcined at 600 °C.

Protective effects of low-temperature plasma on cisplatin-induced nephrotoxicity

The application of atmospheric pressure low-temperature plasma (LTP) in medical treatment has received extensive attention owing to its redox regulatory and anti-inflammatory properties. Nephrotoxicity due to oxidative stress and inflammation is the main adverse effect of cisplatin. In the present study, rats with cisplatin-induced nephrotoxicity were treated with LTP to investigate its potential protective effect. The results showed that LTP treatment has multiple protective effects on cisplatin-induced nephrotoxicity. It significantly improved clinical indicators such as survival rate, water intake, food intake, body weight, and mobility, as well as physiological indexes such as reduced renal index and levels of serum urea, creatinine, and total bilirubin; pathological indicators such as reduced tubular injury, inflammatory infiltration, tubulointerstitial fibrosis, and apoptosis; cell survival indicators such as decreased protein levels of Caspase-3 and Bax and increased Bcl-2; anti-oxidation status such as reduced malondialdehyde content and increased activities of catalase, superoxide dismutase, and glutathione peroxidase; and reduced inflammatory factors such as TNF-α in kidney tissues. Specially, LTP treatment did not influence the anticancer effect of cisplatin as observed in the solid tumor mouse model established by subcutaneously inoculating H22 cells. Moreover, LTP did not influence the physiological and pathological indicators of normal rats, suggesting its biological safety. In conclusion, LTP can protect against cisplatin-induced nephrotoxicity through its anti-oxidation, anti-inflammation, and anti-apoptosis effects, without influencing the anticancer effect of cisplatin.

Generation, Detection and Bio-protection of Reactive Oxygen Species/Free Radicals

In the present paper, generation, detection and protection of reactive oxygen species (ROS)/free radicals in relation to the author's research over about 20 years are reviewed. ROS/free radicals are generally generated physically, chemically and biologically, and they are harmful to living organisms by inducing various disorders and diseases. To prevent the harmful effects of ROS/free radicals, antioxidants are believed to be useful. Among many methods to detect ROS/free radicals, ESR technique is a direct method and is described in detail in this review. Several topics such as the production of ROS/free radicals by low temperature atmospheric pressure plasma, the evaluation of antioxidant activity using hemolysis of erythrocytes and the protective effects of antioxidants against X-ray induced damage to mice, are presented.

Application of Low-Temperature Atmospheric-Pressure Plasma in Metallurgy

Application of Low-Temperature Atmospheric-Pressure Plasma in Metallurgy

Low-Temperature Atmospheric Pressure Plasma Processes for the Deposition of Nanocomposite Coatings

Low-temperature atmospheric pressure (AP) plasma technologies have recently proven to offer a range of interesting opportunities for the preparation of a variety of nanocomposite (NC) coatings with different chemical compositions, structures, and morphologies. Since the late 2000s, numerous strategies have been implemented for the deposition of this intriguing class of coatings by using both direct and remote AP plasma sources. Interestingly, considerable progress has been made in the development of aerosol-assisted deposition processes in which the use of either precursor solutions or nanoparticle dispersions in aerosol form allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. This review summarizes the research published on this topic so far and, specifically, aims to present a concise survey of the developed plasma processes, with particular focus on their optimization as well as on the structural and functional properties of the NC coatings to which they provide access. Current challenges and opportunities are also briefly discussed to give an outlook on possible future research directions.

A Microwave-Induced Atmospheric-Pressure Low-Temperature Linear Plasma Source Based on Parallel Plate Transmission Lines

This article presents a new type of microwave-induced atmospheric-pressure low-temperature dielectric barrier discharge source, based on the principle of parallel plate transmission lines (PPTLs). This source is a simple structure with small size, large plasma discharge area, and low discharge temperature. Experiments show that linear plasma discharge with width of 15 mm can be obtained with input power of only 25 W at 2.45 GHz. The temperature of sample placed 1 mm vertically away from the nozzle and treated for 3 min is about 45 °C even with 60-W microwave input power, which proved its thermal safety even for the biomedical applications. Emission spectroscopy diagnosis indicates that the electron density of plasma can be controlled easily by adjusting the discharge gap and the dielectric thickness. It makes this source available for various applications. This work provides a new approach to obtain uniform linear plasma.

Particle charge distributions in the effluent of a flow-through atmospheric pressure low temperature plasma

Atmospheric pressure low-temperature plasmas are often utilized to perform particle synthesis, treatment, and removal. It is well-known that dust particles are highly negatively charged in these plasmas; however, little is known about dust particle charging behavior as particles leave the plasma volume and pass through the spatial afterglow region. In this work, monodisperse particles of various sizes and work functions were introduced into an atmospheric pressure radiofrequency capacitively coupled flow-through plasma. Dust particle electrical mobility distributions downstream of the flow-through plasma were measured utilizing a differential mobility analyzer in conjunction with a condensation particle counter at various gas flow velocities. Charge distributions were determined from the measured electrical mobility distributions. Experiments confirm that particles become less negatively charged, and even net-positively charged after leaving the plasma volume, with a distribution that follows a shifted Boltzmann charge distribution. Additionally, particle charge in the effluent of the flow-through plasma is negligibly dependent on work function but highly size and flow velocity dependent. Larger particles were shown to have a higher magnitude of charge under all studied conditions; however, particle polarity was switchable by varying gas flow velocity. The charging dynamics were simulated utilizing a constant number Monte Carlo model that accounts for electron temperature decay and the transition from ambipolar to free diffusion of electrons and ions in the spatial afterglow. Simulation results also suggest that, at the same flow velocity, larger particles obtain a greater magnitude of charge, negative or positive. The decrease in electron mobility and the difference between ion and electron convective loss rates create an ion-rich region in the plasma effluent that promotes ion–particle collisions and drives particle charge removal and even reversal of polarity. Larger particles more favorably collide with energetic species in these environments, which results in higher charge states.

Development of Bile Direct Stent Having Antifouling Properties by Atmospheric Pressure Low-Temperature Plasma

Biomimetics (or biomimicry) is a field of technologies based on imitating various functions and properties of organisms. Waterproof products, which are inspired by lotus leaves with super-water-repellent fine structures, are a well-known example of biomimetics. The present study examined the surface structure of snail shells, which exhibit oil repellency (oleophobic property). Snail shells have nanoporous structures with nanoholes on the scale of 200–400 nm. When water enters these nanoholes, the surface is covered by thin water films. The oil can be repelled by the water film. These structures are known as superhydrophilic nanostructures. An earlier report discussed our efforts to create such nanostructures using a nanoimprinting method and assessed the feasibility of application to the inner walls of biliary stents. This involves a labor-consuming two-stage process involving creating nanostructures on a film surface, then rolling the film into a tube. In addition, the nanoimprinting mold made via electron beam lithography is costly and unsuitable for mass production.To overcome these issues, we sought to develop elemental technologies for providing antifouling properties to biliary stents, which are made of polyethylenes (PEs), by forming nanostructures directly on the inner surface, using atmospheric pressure low-temperature plasma. We formed nanostructures on the inner walls of PE tubes of varying diameters under varying plasma conditions. We then examined the resulting structures and effects of the antifouling properties thus imparted.